Binary XML

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For information on the generalized binary file format, see Extensible Binary Meta Language.

Binary XML, or Binary Extensible Markup Language, refers to any specification which defines the compact representation of XML in a binary format. While there are several competing formats, none has been widely adopted by a standards organization or accepted as a de facto standard. Using a binary XML format generally reduces the verbosity of XML documents and cost of parsing ^[1], but hinders the use of ordinary text editors to view and edit the document. Other advantages may include enabling random access and indexing of XML documents.

The major challenge for binary XML is to create a single, widely adopted standard. The World Wide Web Consortium (W3C) has produced the first draft of the EXI format specification, while Sun Microsystems is pushing to have Fast Infoset adopted as an ISO standard. Another standard (ISO/IEC 23001-1), known as Binary MPEG format for XML (BiM), has been standardized by the ISO in 2001. BiM is used by many ETSI standards for Digital TV and Mobile TV. The Open Geospatial Consortium also provides a Binary XML Encoding Specification (currently a Best Practice Paper) optimized for geo-related data (GML).

Alternatives to binary XML include using traditional file compression methods on XML documents (for example gzip); or using an existing standard such as ASN.1. Traditional compression methods, however, offer only the advantage of compression, without the advantage of decreased parsing time or random access. ASN.1 is being used as the basis of Fast Infoset, which is one binary XML standard. There are also hybrid approaches (e.g., VTD-XML) that attach a small index file to an XML document to eliminate the overhead of parsing^[2].

[edit] Binary XML projects and formats

• Efficient XML from AgileDelta, Inc., selected as the basis for the W3C Standard for Binary XML (EXI) [1]
• Extensible Binary Meta Language (EBML) from Matroska
• VTD-XML from XimpleWare and VTD-XML project [2]
• BiM Standard, from the ISO, developed by the MPEG working group
• Fast Infoset Project, from Sun Microsystems [3]
• Binary Characterization Working Group, at W3C [4]
• CBXML, Compact Binary XML, from IBM
• BXML-CWXML, from CubeWerx
• Wireless Binary XML (WBXML)
• Binary XML characterization
• PlainXML project from SourceForge.net
• BXML Encoding Specification [5], a Best Practice Paper [6] from the Open Geospatial Consortium [7]
• MC-NBFX: .NET Binary Format: XML Data Structure [8]

[edit] References